From: Jesper Dangaard Brouer <brouer@redhat.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: brouer@redhat.com, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org,
jakub.kicinski@netronome.com, john.fastabend@gmail.com,
kafai@fb.com, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, songliubraving@fb.com,
syzkaller-bugs@googlegroups.com, yhs@fb.com,
syzbot+4e7a85b1432052e8d6f8@syzkaller.appspotmail.com
Subject: Re: [PATCH bpf-next] xdp: Fix race in dev_map_hash_update_elem() when replacing element
Date: Sun, 8 Sep 2019 13:28:22 +0200 [thread overview]
Message-ID: <20190908132822.5ac2fbe1@carbon> (raw)
In-Reply-To: <20190908082016.17214-1-toke@redhat.com>
On Sun, 8 Sep 2019 09:20:16 +0100
Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> syzbot found a crash in dev_map_hash_update_elem(), when replacing an
> element with a new one. Jesper correctly identified the cause of the crash
> as a race condition between the initial lookup in the map (which is done
> before taking the lock), and the removal of the old element.
>
> Rather than just add a second lookup into the hashmap after taking the
> lock, fix this by reworking the function logic to take the lock before the
> initial lookup.
>
> Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
> Reported-and-tested-by: syzbot+4e7a85b1432052e8d6f8@syzkaller.appspotmail.com
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
prev parent reply other threads:[~2019-09-08 11:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 20:08 general protection fault in dev_map_hash_update_elem syzbot
2019-09-05 21:44 ` Alexei Starovoitov
2019-09-06 12:54 ` Jesper Dangaard Brouer
2019-09-06 23:04 ` Toke Høiland-Jørgensen
2019-09-08 1:59 ` syzbot
2019-09-08 8:20 ` [PATCH bpf-next] xdp: Fix race in dev_map_hash_update_elem() when replacing element Toke Høiland-Jørgensen
2019-09-08 11:28 ` Jesper Dangaard Brouer [this message]
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